1. Field
The present invention relates to a lithographic apparatus and a method for manufacturing a device.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of flat panel displays, integrated circuits (ICs), and other devices involving fine structures. In a conventional apparatus, a patterning device, which can be referred to as a mask or a reticle, can be used to generate a circuit pattern corresponding to an individual layer of a flat panel display or other device. This pattern can be transferred onto a target portion (e.g., comprising part of one or several dies) on a substrate (e.g., a glass plate). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (e.g., resist) provided on the substrate.
Instead of a circuit pattern, the patterning device can be used to generate other patterns, for example a color filter pattern or a matrix of dots. Instead of a mask, the patterning device can comprise a patterning array that comprises an array of individually controllable elements. An advantage of such a system compared to a mask-based system is that the pattern can be changed more quickly and for less cost.
The size of an array of individually controllable elements can be limited due to the difficultly in manufacturing a large array with adequate quality and the difficulty in providing sufficient control lines to a large array in order to set patterns on it. Thus, several such arrays of individually controllable elements can be used within a single lithographic apparatus to pattern the substrate. It is desirable that the arrays of individually controllable elements are aligned relative to the remainder of the apparatus and each other to within predetermined tolerances. In order to set the pattern on the arrays of individually controllable elements, each element is actuated and the requisite control signals are supplied to the arrays. Consequently, heat is generated in the arrays of individually controllable elements, which is not generated in a conventional mask or reticle. Such heat can result in thermal expansion within the lithographic apparatus, which can affect the alignment of the arrays of individually controllable elements relative to the lithographic apparatus and relative to each other.
Therefore, what is needed is a system and method for securing arrays of individually controllable elements to a lithographic apparatus that can ensure that a position of the arrays is within a required tolerances.